Driver circuits are usually required to switch semiconductor switches on and off in accordance with a (usually binary) control signal which may be provided, e.g., by a micro-controller or similar control circuits. For this purpose the control signal is supplied to the driver circuit that is configured to generate a corresponding driver signal which is supplied to the control electrode of a semiconductor switch and appropriate to switch the semiconductor switch on and off. The driver circuit may also be configured to generate the driver signals such that the switching behavior of the switch matches a specific desired behavior. For example, by generating appropriate driver signals the steepness of the edges of the switched current and/or voltage can be specifically influenced. This “edge shaping” capability is often required to fulfill specific requirements concerning electromagnetic emissions (EMI) and electromagnetic compatibility (EMC).
The mentioned control circuits (e.g., micro controllers) generate the control signal (or a plurality of control signals, one for each semiconductor switch to be controlled) in such a manner that the resulting switching operation corresponds to a desired switching pattern. The control signals are usually binary signals having only two signal levels, namely a low level (logic “0”) and a high level (logic “1”). However, the actual potential (in volts) of a “low level” and a “high level” is different for different types of control circuits. For example, a low level may correspond to a potential of 0 volts whereas a high level may correspond to 3.3 volts, 5 volts, 12 volts, or even 15 volts dependent on the employed control circuit. Some control circuits use negative voltages to indicate a low level, e.g., −15 volts, whereas a high level is indicated by +15 volts. Thus, an absolute definition of the control signal levels is usually not possible.
As a consequence, the input signal specification of the driver circuits (e.g., gate driver) must usually match the output signal specification of the control circuit (e.g., micro controller). Thus there is a need for driver circuits for driving semiconductor switches which are capable of processing a wide range of control signal levels.